Examples of known miniature photoflash lamps are described in U.S. Pat. Nos. 3,817,683 (Weber) and 3,893,798 (Sterling). Such lamps typically include an all-glass envelope, electrical ignition means including a pair of lead-in wires spacedly oriented within a base of the envelope with each wire having a quantity of primer material located on an end thereof and joined to the other primer material by a linear electrical filament, a quantity of shredded, combustible foil (e.g., zirconium, aluminum, hafnium, or thorium), and a pressurized, combustion-supporting atmosphere (e.g., oxygen) within the envelope. Understandably, it is essential that the envelope is hermetically sealed in order to contain the atmosphere and assure operability of the lamp.
It will be understood from the following that one of the primary objects of the instant invention is to provide a new and unique photoflash lamp which eliminates the need for the aforedescribed sealed glass envelope and shredded foil elements, as well as the pressurized atmosphere associated therewith, while still providing an intense light output more than sufficient to meet the requirements of many of today's higher speed films. The lamp as defined herein is thus much less expensive to manufacture than existing miniature lamps and also has proven both safe and reilable in operation.
Prior to development of the above, known miniature lamps, photoflash lamps were produced which did not require shredded foil or similar combustible materials but instead utilized a flash-producing material such as a combination of zirconium and an oxidant (e.g., potassium chlorate, barium nitrate, or strontium nitrate). One such example is described in U.S. Pat. No. 3,220,224 (Baird). It was believed essential in these products, however, that the particle size of the flash-producing material (particularly that of the zirconium) must be very small or "finely divided". As described in U.S. Pat. No. 3,220,224, the optimum particle size for the zirconium is approximately 1.8 microns while that of the oxidant should not exceed 8.5 microns (optimum being 4-5.5 microns). It was also deemed essential that the ratio of flash-producing material to total internal volume of the lamp's envelope remain small for safety purposes. Accordingly, these earlier lamps required relatively large envelopes (e.g., 7-8 cubic centimeters) to accommodate the correspondingly large quantities of flash-producing material necessary for adequate light output and were not, therefore, adaptable to miniaturization and the advantages inherent therewith.
It is believed, therefore, that a miniature photoflash lamp which can provide the several advantages cited above without adversely affecting safety, manufacture, or light output would constitute a significant advancement in the art.